WebView jump to anchor using loadDataWithBaseUrl

How about control it by JavaScript? I didn't try it but maybe this is a clue.

builder.append(getThreadBody());
builder.append("<script>window.location.hash="949823";</script>");
builder.append("</body></html>");

Remember enable javascript for WebView.

----Additional Answer----

I saw that you use TimerTask to load the javascript, That works but I think there is another better way. WebView have a callback named onPageFinished and it will be trigger when WebView finish loading webpage. You could inject your JS there.

webContents.setWebViewClient(new WebViewClient(){

    @Override
    public void onPageFinished(WebView view, String url) {
          String id = "895884";
          webContents.loadUrl("javascript:scrollAnchor(" + id + ");");
    }

});

Hope this is useful!

First of all, you don't need to use javascript. If you loaded content with

webContents.loadDataWithBaseURL("some://dummy/url",...);

you can simply scroll to anchor with

webContents.loadUrl("some://dummy/url#anchor");

Secondly, doing that on onPageFinished without additional control results in never ending loop! When loadUrl finishes onPageFinished get's called again and again.